Mongoose in the rainforest: Analyzing population estimates and habitat attributes for a better management strategy in El Yunque National Forest

Background/Question/Methods

The small Indian mongoose, Herpestes auropunctatus, was introduced throughout most of the Caribbean and Pacific Islands by then end of the 19^th century in order to control rat populations (Rattus sp.) in sugar cane plantations. Mongooses failed to suppress rat populations and in turn have significantly altered the food web in forests, becoming detrimental to other species and a vector for rabies virus. In El Yunque National Forest (YNF) in Puerto Rico, current management plans to control mongoose populations include the removal of individuals seasonally from human-frequented areas, but populations remain stable range-wide. The objectives of this study were: 1) to estimate mongoose abundance in four different forest types of YNF and an adjacent coastal site (NEC), and 2) to relate observed variation in mongoose abundance with habitat attributes. 

Results/Conclusions

We used Capture-Mark-Recapture assuming a closed population in YNF and NEC. We established five capture nights per week during the summer of 2012. A total of 34 individuals were captured with 4 recaptures. An estimate of the population size was derived from four competing models (M₀, M_b, M_hChao, M_bh). Selected by AIC values and after bias correction, M_b (behavioral) model predicted an abundance of 44 individuals (SE 9.9) in YNF versus an estimation of 141 individuals in the costal forest adjacent to YNF. Among the four habitat types of YNF, habitats dominated by Sierra Palm (Prestoea montana) accounted for the largest population. Mongoose abundance was greater on those sites of lower elevation and human-frequented areas. Multiple regression analysis was performed in order test if vegetation cover and coarse woody debris can significantly predict captures frequencies throughout the park and coastal forest.  The regression indicated that none of the factors explained capture frequencies for this study (R²=0.05, F(3,70)=1.331, p=0.3. Correct population estimatimates coupled with GIS data available for YNF, will provide managers with information on mongoose population structure, dispersal through the landscape, and demography at various spatial scales.